The Quantitative Models, Analysis, and Epidemiology Core will provide leadership, consultation, support services, and training to CAIR investigators and scientific personnel in the areas of biostatistics, research design, analysis, and epidemiology. In addition, the Core will stimulate and provide leadership in the conduct of cross-study or combined-project data analyses, as well as interact with other CAIR cores in matters related to quantitative models, design and analysis, and epidemiological aspects of projects within those cores. Scientists in the Quantitative Core will also develop, supervise and manage a program- wide participant database, which will be an important resource for the conduct of cross-study intervention outcome analyses, estimating the effect sizes produced by different types of behavior change interventions employed in individual CAIR studies, and performing cost-benefit analysis that can estimate magnitude of behavior produced-- and new HIV infections that can prevent-- through the application of behavior change interventions of differing intensities and costs with populations vulnerable to IV infection. Scientists in the Quantitative Core will perform these activities in a variety of ways including the development of Center-wide facilities and procedures for data including the development of Center-wide facilities and procedures for data management, consultation to individual CAIR investigators and project investigational teams, collaboration with scientists in other CAIR cores to initiate and support research activities, performance of cross-study analysis, participation in Center scientific planning and decision-making, and participation in CAIR Conferences, research seminars, and other research training activities.